ES2999862T3 - Method for installing an extension tube in a nuclear reactor - Google Patents

Abstract

Disclosed are arrangements and devices for reducing and/or preventing wear on a thermal sleeve in a nuclear reactor. The arrangements include a first structure disposed on or in one of the thermal sleeves and a second structure disposed on or in the head penetration adapter. At least a portion of the first structure and at least another portion of the second structure interact to resist, reduce, and/or prevent rotation of the thermal sleeve about its central axis relative to the head penetration adapter. The devices include a base for coupling to a reactor guide tube and a plurality of protruding members extending upwardly from the base. Each member has a portion for coupling to a corresponding portion of a guide funnel of the thermal sleeve. (Automatic translation with Google Translate, no legal value)

Description

Description

Method for installing an extension tube in a nuclear reactor

BACKGROUND

In a nuclear reactor, thermal sleeves serve four purposes. The thermal sleeve protects the rod bundle control assembly (RCCA) drive rod from the effects of the fluid present in the reactor vessel head plenum (e.g., crossflow). The thermal sleeve facilitates hydraulic communication (flow to the CRDM) during RCCA insertion (control rod drop). The thermal sleeve provides control rod alignment for vessel head installation. The thermal sleeve also protects the CRDM head and shell penetration from reactor coolant thermal transients.

Thermal sleeves include an outer diameter (OD) and an inner diameter (ID) and include flanges. Thermal sleeves are subject to wear at the flanges and on the outer and inner diameters. Thermal sleeves have been observed to wear between the top header and the CRDM penetration housing in a nuclear reactor. This wear has been measured using laser metrology to determine the amount of "drop" a given thermal sleeve has experienced.

Thermal sleeve OD/ID and flange wear generates recurring maintenance costs. Thermal sleeve failure due to OD/ID wear requires costly repair before power can be restored. Wear predictions through Pressurized Water Reactor Owners Group (PWROG) programs can be used to identify which sleeves will eventually require intervention. Proactive removal of thermal sleeves can eliminate or significantly delay future thermal sleeve inspections for wear.

A method has been developed to remove a worn thermal sleeve and replace it with a temporary "compressible thermal sleeve." This method does not require removing the CRDM engine assembly from the top side of the reactor head.

However, the method does not address the failure mechanism due to wear of the thermal sleeve and the CRDM penetration casing. Therefore, it is highly likely that even a compressible thermal sleeve will continue to wear along with the CRDM penetration casing.

In response to the functional experience of thermal sleeve wear at various nuclear plants, there is a clear need to eliminate the thermal sleeves used in nuclear reactors. During inspections of nuclear reactors, wear has been identified on the thermal sleeve flanges and/or inner/outer diameters. Furthermore, there is a need to replace the thermal sleeves with extension tubes attached directly to the nuclear reactor's CRDM penetration casing. Consequently, there is a significant and repeated need for permanent thermal sleeve replacement to eliminate the need for multiple and varied thermal sleeve inspections over time.

US 2019/252082 A1 discloses a prior art method for replacing a damaged thermal sleeve on a reactor vessel head adapter that connects a control rod drive mechanism to a reactor vessel head.

SUMMARY

In one aspect, the present disclosure provides a method for installing an extension tube in a nuclear reactor comprising a housing (CRDM) for a control rod drive mechanism with a threaded head penetration nozzle and a thermal sleeve disposed therein. The method comprises removing the thermal sleeve from the threaded head penetration nozzle and aligning the extension tube with the threaded end of the head penetration nozzle. The extension tube comprises a threaded end and a non-threaded end, the threaded end being sized and configured to threadably engage the threaded head penetration nozzle. The method further comprises screwing the threaded end of the extension tube onto the threaded end of the threaded head penetration nozzle, applying a tightening torque on the extension tube to the threaded end of the threaded head penetration nozzle, calibrating the alignment of the extension tube with respect to the threaded head penetration nozzle, installing retaining weld beads between the extension tube and the threaded end of the threaded head penetration nozzle, and installing a guide funnel on the unthreaded end of the extension tube.

In one aspect, the present disclosure provides a method for installing an extension tube in a nuclear reactor comprising a control rod drive mechanism (CRDM) housing with an unthreaded head penetration nozzle and a heat sleeve disposed therein. The method comprises removing the heat sleeve from the unthreaded head penetration nozzle, machining the unthreaded head penetration nozzle from the CRDM housing, installing and aligning a threaded adapter to the machined end of the unthreaded head penetration nozzle of the CRDM housing, joining the threaded adapter to the machined end of the unthreaded head penetration nozzle of the CRDM housing, machining a bore defined by the unthreaded head penetration nozzle of the CRDM housing, machining a bore defined by the threaded adapter, machining an outside diameter of a joint between the machined end of the unthreaded head penetration nozzle of the CRDM housing and the threaded adapter, installing the extension tube in the threaded adapter, and installing retaining weld beads between the extension tube and the threaded adapter.

In addition to the foregoing, various other aspects of the product of the method and/or system and/or program are set forth and described in the teachings such as text (e.g., claims and/or detailed description) and/or drawings of the present disclosure.

The foregoing is a summary and therefore may contain simplifications, generalizations, inclusions, and/or omissions of details; accordingly, those skilled in the art will appreciate that the summary is illustrative only and is NOT intended to be limiting in any way. Other aspects, features, and advantages of the devices and/or processes and/or other subjects described herein will become apparent in the teachings presented herein.

In one or more diverse aspects, related systems include, but are not limited to, circuitry and/or programming for effecting the method aspects referenced herein; the circuitry and/or programming may be virtually any combination of hardware, software, and/or firmware configured to affect the method aspects referenced herein depending on the design choices of the system designer. In addition to the foregoing, various other aspects of the method and/or system are set forth and described in the teachings such as text (e.g., claims and/or detailed description) and/or drawings of the present disclosure.

Furthermore, it shall be understood that any one or more of the following forms, expressions of forms and examples may be combined with any one or more of the following forms, expressions of forms and examples described.

The foregoing summary is illustrative only and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments, and features described above, other aspects, embodiments, and features will become apparent upon reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the disclosed forms are particularly set forth in the appended claims. The disclosed forms, however, both in terms of organization and methods of operation, can be better understood by reference to the following description, taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic cross-sectional view of an upper region of a conventional nuclear reactor, in accordance with at least one aspect of the present disclosure.

FIG. 2 is a schematic cross-sectional view of a conventional reactor vessel head penetration illustrating a CRDM housing, a head penetration nozzle, and a thermal sleeve, in accordance with at least one aspect of the present disclosure.

FIG. 3 is a sectional view of a thermal sleeve and a CDRM housing in an unworn state, in accordance with at least one aspect of the present disclosure.

FIG. 4 is a sectional view of a thermal sleeve and a CDRM housing in a substantially worn condition, in accordance with at least one aspect of the present disclosure.

FIG. 5 a sectional view of a thermal sleeve and a CDRM housing in a worn state up to the point of separation of the thermal sleeve, according to at least one aspect of the present disclosure.

FIG. 6 illustrates an extension tube that may be installed in a nuclear reactor in place of thermal sleeves, in accordance with at least one aspect of the present disclosure.

FIG. 7 illustrates an extension tube that can be installed in the nuclear reactor in place of thermal sleeves, in accordance with at least one aspect of the present disclosure.

FIG. 8 is a schematic cross-sectional view of an upper region of a conventional nuclear reactor illustrating a portion of a reactor vessel head penetrated by a plurality of head penetration nozzles extending downwardly from a CRDM housing, in accordance with at least one aspect of the present disclosure.

FIG. 9 is a sectional view of the threaded penetration adapter shown in FIG. 8 coupled between the extension tube and the headed penetration nozzle, in accordance with at least one aspect of the present disclosure.

FIG. 10 is a sectional view of a penetration nozzle with head with extension tube, according to at least one aspect of the present disclosure.

FIG. 11 is a sectional view of the headed penetration nozzle shown in FIG. 10 positioned through the head of the reactor vessel, in accordance with at least one aspect of the present disclosure. FIG. 12 is a sectional view of the headed penetration nozzle shown in FIGS. 10 and 11 with an extension tube attached thereto, in accordance with at least one aspect of the present disclosure. FIG. 13 is a perspective view of a compressible guide sleeve, which is received in the space defined by the headed penetration nozzle shown in FIG. 12, in accordance with at least one aspect of the present disclosure.

FIG. 14 illustrates an extension tube shown in FIGS. 8-10 and 12 with a guiding funnel and a threaded penetration adapter, in accordance with at least one aspect of the present disclosure.

FIG. 15 is a process for removing a thermal sleeve shown in FIGS. 3-5 that needs to be removed, in accordance with at least one aspect of the present disclosure.

FIG. 16 is a process for installing a threaded extension tube, in accordance with at least one aspect of the present disclosure.

FIG. 17 illustrates an extension tube comprising a threaded penetration adapter aligned with a threaded headed penetration nozzle extending through a reactor vessel head, in accordance with at least one aspect of the present disclosure.

FIG. 18 illustrates the extension tube and threaded head penetration nozzle shown in FIG. 17 threadedly coupled, in accordance with at least one aspect of the present disclosure.

FIG. 19 illustrates tightening the extension tube to the headed penetration nozzle shown in FIG. 18 using a torque tool, in accordance with at least one aspect of the present disclosure.

FIG. 20 illustrates applying a torque to the extension tube to the headed penetration nozzle shown in FIG. 18 using a torque tool, in accordance with at least one aspect of the present disclosure.

FIG. 21 is a sectional view of an extension tube alignment calibration test setup, in accordance with at least one aspect of the present disclosure.

FIG. 22 is a perspective view of a gauge used in the calibration process of the extension tube alignment calibration test setup shown in FIG. 21, in accordance with at least one aspect of the present disclosure.

FIG. 23 is a sectional view of the alignment of an actuating rod with respect to the extension tube, in accordance with at least one aspect of the present disclosure.

FIG. 24 illustrates retaining weld beads installed between the threaded end of the headed penetration nozzle shown in FIG. 18 and the threaded penetration adapter coupled to the extension tube by a weld shown in FIG. 18, in accordance with at least one aspect of the present disclosure.

FIG. 25 illustrates three-leaf compressible flexible sections of the compressible guide sleeve shown in FIG. 13 in a compressed configuration to contract the flanges of the compressible flexible sections to a size suitable for insertion into the guide funnel, according to at least one aspect of the present disclosure.

FIG. 26 illustrates a compression tool that can be used to compress the compressible guide sleeve shown in FIG. 25 prior to inserting the compressible guide sleeve into the guide nozzle, in accordance with at least one aspect of the present disclosure.

FIG. 27 illustrates the compressible guide sleeve shown in FIG. 25 in its compressed configuration inserted through the headed penetration nozzle and the CRDM head adapter, in accordance with at least one aspect of the present disclosure.

FIG. 28 illustrates the compressible flexible sections of the compressible guide sleeve shown in FIG. 27 released such that the flanges of the compressible flexible sections engage the shoulder of the countersunk hole defined within the CRDM head adapter section of the headed penetration nozzle, in accordance with at least one aspect of the present disclosure.

FIG. 29 illustrates the compressible guide sleeve shown in FIG. 28 in its final installed state, in accordance with at least one aspect of the present disclosure.

FIG. 30 is a sectional view of the reactor vessel head illustrating the extension tube coupled to the headed penetration nozzle installed within the reactor vessel head, in accordance with at least one aspect of the present disclosure.

FIG. 31 is a detailed view of the installed extension tube that is coupled to the head penetration nozzle shown in FIG. 30 showing the extension tube retaining welds, in accordance with at least one aspect of the present disclosure.

FIG. 32 is a sectional view of the extension tube coupled to the head penetration nozzle installed within the reactor vessel head shown in FIG. 31, in accordance with at least one aspect of the present disclosure.

FIG. 33 is an elevation view of the extension tube coupled to the head penetration nozzle installed within the reactor vessel head shown in FIG. 32, in accordance with at least one aspect of the present disclosure.

FIG. 34 illustrates a threaded-head penetration nozzle that is unusable due to wear, damage, or size mismatch, in accordance with at least one aspect of the present disclosure. FIG. 35 is a sectional view of the headed penetration nozzle shown in FIG. 34, in accordance with at least one aspect of the present disclosure.

FIG. 36 is a process for installing an extension tube into a non-threaded CRDM housing, in accordance with at least one aspect of the present disclosure.

FIG. 37 is a sectional view of a threadless CRDM housing prior to machining, in accordance with at least one aspect of the present disclosure.

FIG. 38 is a sectional view of the threadless CRDM housing shown in FIG. 37 after machining, in accordance with at least one aspect of the present disclosure.

FIG. 39 is a detailed sectional view of the threadless CRDM housing shown in FIG. 38, in accordance with at least one aspect of the present disclosure.

FIG. 40 illustrates a threaded adapter comprising male threads sized and configured to receive female threads of the extension tube shown in FIG. 14 and an unthreaded end configured to abut the machined end face of the unthreaded CRDM housing shown in FIGS. 38-39, in accordance with at least one aspect of the present disclosure.

FIG. 41 illustrates a space defined between the machined end face of the unthreaded CRDM housing and the unthreaded end of the threaded adapter shown in FIGS. 38-40, in accordance with at least one aspect of the present disclosure.

FIG. 42 illustrates the threaded adapter and non-threaded CRDM housing shown in FIG. 41 in a joined configuration, in accordance with at least one aspect of the present disclosure.

FIG. 43 illustrates machined holes defined by the unthreaded CRDM housing and the threaded adapter shown in FIG. 42, in accordance with at least one aspect of the present disclosure.

FIG. 44 illustrates a machined/ground OD of the joint shown in FIGS. 42-43, in accordance with at least one aspect of the present disclosure.

FIG. 45 illustrates the joined threaded adapter and unthreaded CRDM housing shown in FIGS. 38-44 installed below the reactor vessel head and ready to receive the extension tube, in accordance with at least one aspect of the present disclosure.

FIG. 46 illustrates the joined threaded adapter and unthreaded CRDM housing shown in FIGS. 38-45 installed below the reactor vessel head and ready to receive the extension tube, in accordance with at least one aspect of the present disclosure.

FIG. 47 illustrates the extension tube threaded adapter installed in the threaded adapter attached to the unthreaded CRDM housing as shown in FIGS. 38-46 from below the reactor vessel head, in accordance with at least one aspect of the present disclosure.

FIG. 48 illustrates retaining weld beads between the threaded adapter of the extension tube and the threaded adapter of the unthreaded CRDM housing shown in FIGS. 38-47, in accordance with at least one aspect of the present disclosure.

DETAILED DESCRIPTION

This application is related to PCT/US2020/019116, filed on 2020-02-20, entitled ANTI-ROTATION PROVISIONS FOR THERMAL SLEEVES.

Before explaining in detail various aspects of methods for removing thermal sleeves in nuclear reactors, or more particularly, methods for replacing thermal sleeves with extension tubes that are directly attached to the penetration casings (CRDMs) of the nuclear reactor control rod drive mechanism, it should be emphasized that the illustrative aspects are not limited in their application or use to the details of construction and arrangement of the parts illustrated in the accompanying drawings and description. The illustrative aspects may be implemented or incorporated into other aspects, variations and modifications, and may be practiced or carried out in a variety of ways. Furthermore, unless otherwise indicated, the terms and expressions used herein have been chosen for the purpose of describing the illustrative aspects for the convenience of the reader and not for purposes of limitation.

Furthermore, it is understood that any one or more of the following forms, expressions of forms and examples may be combined with any one or more of the following forms, expressions of forms and examples described.

In one aspect, the present disclosure is directed, as previously discussed, to methods for removing thermal sleeves in nuclear reactors. In another aspect, the present disclosure is directed to methods for replacing thermal sleeves with extension tubes that are directly attached to the CRDM penetration housings of the nuclear reactor. In one aspect, the thermal sleeve can be removed from below the reactor vessel closure head (RVCH) using existing equipment and processes for thermal sleeve removal. An extension tube is installed, which connects directly to the CRDM penetration housing. According to one aspect, there are two primary components required to remove a thermal sleeve. First is the extension tube and second is the upper guide sleeve. The purpose of the upper guide sleeve is to provide final guidance for the drive rod within the CRDM through the closure stop plate.

Generally speaking, there are two styles of CRDM penetration housings: threaded and unthreaded. Threaded penetrations have a 95.25 mm (3 3/4”) UN-2A thread. Unthreaded penetrations have a bare tubular end with radii on both the outside and inside diameters to accommodate transitions.

For threaded penetrations, an extension tube can be manufactured to a specific length that would establish a funnel height equal to that of existing thermal sleeves when threaded and tightened. For unthreaded penetrations, a penetration nipple can be welded to the penetration, which would then provide the appropriate male thread for connecting the extension tube.

A special compressible guide sleeve (CGS) has been designed to provide the same functions as the guide sleeve in the replacement RVCH and AP1000 pressurized water reactors, for example. The CGS can be installed from underneath the RVCH, along with the extension tube. The present disclosure provides a new and innovative process for retrofitting an extension tube in an in-service RVCH.

Heated sleeves showing wear at the flanges and/or ID/OD are suitable candidates for removal and replacement with extension tubes to eliminate recurring maintenance costs and breakdowns that require costly repairs before power can be restored. Wear predictions through PWROG programs can be used to identify which heat sleeves will eventually require intervention. Proactive removal combined with engineering justification can eliminate or significantly delay future heat sleeve inspections for many types of wear.

FIG. 1 is a schematic cross-sectional view of an upper region of a conventional nuclear reactor 2 illustrating a portion of a reactor vessel 4 penetrated by a plurality of headed penetration nozzles 6 extending downwardly from a CRDM housing 8. FIG. 2 is a schematic cross-sectional view of a headed penetration of a conventional reactor vessel illustrating a CRDM housing 8, a headed penetration nozzle 6, and a thermal sleeve 10. With continuing reference to FIG. 1 , as well as the sectional view of FIG. 2, a thermal sleeve 10 including a guide funnel 12 is positioned within each headed penetration nozzle 6 below each CRDM housing 8 such that each guide funnel 12 is positioned directly above, and spaced a distance from, a corresponding guide tube 14 extending from an upper support plate 16 within the reactor vessel 4. The thermal sleeve 10 is housed within the headed penetration nozzle 6 within the reactor vessel 4 except within region 15 (FIG. 2) where the thermal sleeve 10 is exposed to the reactor coolant.

It is presently believed that wear of the thermal sleeve 10 and the headed penetration nozzle 6 in the region 13 illustrated in FIGS. 1 and 2 results from rotation of the thermal sleeve 10 within the headed penetration nozzle 6 about a central axis 18 of the thermal sleeve 10. It is believed that vortices in reactor coolant flowing within the reactor vessel 4 come into contact with the thermal sleeve 10 (i.e., in region 15), causing the thermal sleeve 10 to rotate about its central axis 18 relative to the headed penetration nozzle 6.

The present disclosure provides methods for removing thermal sleeves 10 in a nuclear reactor 2, and more particularly, methods for replacing thermal sleeves 10 in a nuclear reactor 2 with extension tubes directly attached to a CRDM penetration housing 6 of the nuclear reactor 2. These methods fully satisfy the strong and repeated need for permanent replacement of the thermal sleeve 10 to eliminate the need for multiple and varied inspections of the thermal sleeve 10 over time. FIG. 3 is a sectional view 100 of a thermal sleeve 110 and a CDRM housing 108 in an unworn state. The thermal sleeve 110 includes a flange 112 defining an outer diameter 114 (OD) and an inner diameter 116 (ID) that are subject to wear. The thermal sleeve 110 is subject to wear between the upper header and the CRDM penetration housing 108 in a nuclear reactor.

FIG. 4 is a sectional view 120 of the thermal sleeve 110 and the CDRM housing 108 in a substantially worn condition. As previously discussed, the thermal sleeve 110 shows substantial wear at the shoulder 112 and at the outer diameter 114 and inner diameter 116. This wear may be manifested by a drooping of the thermal sleeve 110.

FIG. 5 is a sectional view 140 of the thermal sleeve 110 and the CDRM housing in a worn state to the point of separation of the thermal sleeve 110. As shown, the thermal sleeve 110 has developed a tear 118 resulting in separation of the thermal sleeve 110. The sectional view 140 also shows additional wear of the shoulder 112, OD 114 and ID 116 relative to the sectional view 120 shown in FIG. 4.

Referring to FIGS. 1-5, the extension tubes can be adapted to a variety of reactor vessel heads 4 (FIG. 1) that currently have thermal sleeves 10 (FIGS. 1-2), 110 (FIGS. 3-5) installed. Typical CRDM penetration designs have “threaded” or “unthreaded” ends that protrude through the reactor vessel head 4. Referring also to FIG. 6, an extension tube 200 is shown that can be installed in the nuclear reactor 4 in place of the thermal sleeves 10, 110. The extension tube 200 comprises a substantially cylindrical body 202 and a threaded end 204 that would protrude through the reactor vessel head 4 once installed and threadably engage the threaded penetration nozzle. FIG. 7 illustrates an extension tube 240 that may be installed in the nuclear reactor 4 in place of the thermal sleeves 10, 110. The extension tube 240 comprises a substantially cylindrical body 242 and an unthreaded end 244 that would protrude through the head of the reactor vessel 4 once installed and would be coupled to an unthreaded penetration nozzle by suitable welding, for example.

FIG. 8 is a schematic cross-sectional view of an upper region of a conventional nuclear reactor 302 illustrating a portion of a reactor vessel head 304 penetrated by a plurality of headed penetration nozzles 306 extending downwardly from a CRDM housing 308. An extension tube 310 is coupled to the distal end 314 of the headed penetration nozzle 306. The distal end 316 of the extension tube includes a guide funnel 312. The headed penetration nozzles 306 include a compressible guide sleeve 318. A threaded penetration adapter 320 is coupled between the extension tube 310 and the headed penetration nozzle 306. In one aspect, the threaded penetration adapter 320 is employed for unthreaded penetration nozzles 306 to facilitate installation of the extension tube 310 into an unthreaded headed penetration nozzle 306. The threaded penetration adapter 320 is welded to the end of the unthreaded headed penetration nozzle 306. The compressible guide sleeves 318 are described in more detail in commonly owned patent application number PCT/US2019/015797, filed on 01/30/2019, entitled THERMAL SLEEVE.

FIG. 9 is a sectional view of threaded penetration adapter 320 coupled between extension tube 310 and headed penetration nozzle 306. Threaded penetration adapter 320 includes a body 322 with an upper end adapted and configured to couple to the unthreaded end of headed penetration nozzle 306 and a lower end adapted and configured to couple to extension tube 310. In one aspect, the upper end of body 322 of threaded penetration adapter 320 may be welded to unthreaded headed penetration nozzle 306 at connection 324 and the lower end of threaded adapter body 322 may be welded to extension tube 310 at connection 326. In one aspect, connection 326 is a bi-metal weld on extension tube 310 to transition to steel. In various aspects, the threaded penetration adapter 320 may include threads for threadably coupling to the non-threaded head penetration nozzle 306 and/or extension tube 310, for example.

FIG. 10 is a sectional view of a headed penetration nozzle 306 with extension tube 310. The headed penetration nozzle 306 extends downwardly from a closure housing 336 and penetrates the reactor vessel head 304. The closure housing 336 contains a CRDM motor 330 and a compressible guide sleeve 332. The closure housing 336 is coupled to the headed penetration nozzle 306 via a bi-metal weld 334. The headed penetration nozzle 306 is coupled to an extension tube 310 within the reactor vessel head 304 via a threaded penetration adapter 320. The extension tube 310 is coupled to a guide funnel 312. As shown in FIG. 10, the heat sleeve on the headed penetration nozzle 306 has been replaced by the extension tube. 310.

FIG. 11 is a sectional view of the headed penetration nozzle 306 located through the reactor vessel head 304. The end of the headed penetration nozzle outside the reactor vessel head 304 comprises a CRDM headed adapter 337. The headed penetration nozzle 306 defines a space 338, which normally contains a thermal sleeve that is not.

FIG. 12 is a sectional view of the headed penetration nozzle 306 with the extension tube 310. The headed penetration nozzle 306 is coupled to the extension tube 310 via an optional threaded penetration adapter 320. The compressible guide sleeve 332, shown in detail in FIG. 14, is typically contained within a space 340 defined by the headed penetration nozzle 306.

FIG. 13 is a perspective view of a compressible guide sleeve 332, which is received in the space 340 defined by the headed penetration nozzle 306, as shown in FIG. 12. The compressible guide sleeve 332 comprises a three-bladed, compressible flexible section 342 to achieve compressibility and rigidity. In various aspects, the compressible guide sleeve may comprise at least two and more than three compressible sleeves. Each of the compressible flexible blade sections 342 includes a flange 344 that is positioned within the CRDM housing 308. The compressible guide sleeve 332 is installed in the CRDM penetration to facilitate guiding the drive rod into the closure housing 336 (FIG. 10). The lower end of the compressible guide sleeve 332 comprises an alignment feature 346. Existing thermal sleeve eliminator modifications in new RVCHs employ a smaller guide sleeve similar to a truncated thermal sleeve. The purpose of the guide sleeve is to provide guidance for the drive rod within the CRDM closure assembly. The compressible guide sleeve 332 serves the same function as the guide sleeve and is installed from below the reactor vessel head 304 (FIGS. 8-12), after the extension tube 310 has been attached to the headed penetration nozzle 306. While the design of the compressible guide sleeve 332 allows it to be flexible enough to be installed through the CRDM penetration, it is also rigid enough to require a specialized fixture to compress the compressible guide sleeve 332 prior to installation. This rigidity is sufficient to remain in place during all basic design conditions of a nuclear plant.

The entire installation process for the extension tube 310 is performed below the RVCH and requires no modifications or removal of the CRDM, nor any modifications to the upper internal components. The installation processes below the header are known and have been developed by the licensee of this application. Replacing the thermal sleeve with the entire extension tube 310 eliminates any future wear of the thermal sleeve at the installation location. The extension tube 310 does not require wear inspections during its useful life.

FIG. 14 illustrates an extension tube 310 with a guide funnel 312 and a threaded penetration adapter 320. In one aspect, the guide funnel 312 is collapsible and configured to fail before CRDM or fuel damage can occur in the event of misalignment during header installation. In one aspect, the threaded penetration adapter 320 includes a threaded end with female threads 348 for threadably engaging the male threads 349 (FIG. 17) of the headed penetration nozzle 306 (FIGS. 8-13). During the heat sleeve replacement process, retaining weld beads 352 are provided between the threaded penetration adapter 320 and the headed penetration nozzle 306 to stabilize the connection. The threaded penetration adapter 320 is coupled to the extension tube 310 by a weld 354. The extension tube 310 is coupled to the guide funnel 312 by retaining weld beads 356.

FIG. 15 is a process 400 for removing a thermal sleeve that needs to be removed. Next, the process 400 will be described with reference to FIGS. 1-5 and 15. The thermal sleeve 10 (FIGS. 1-2), 110 (FIGS.

3-5) that needs to be removed is identified 402. The heat sleeve ID 10, 110 is shaken and cleaned 404. The electrical discharge machining (EDM) head is installed 406 on a section of the heat sleeve 10, 110 and a series of cuts are made. After the series of cuts is completed, the heat sleeve 10, 110 is removed 408 and the headed penetration nozzle 306 is cleaned and inspected 410. Removal of the heat sleeve 10, 110 is now complete 412.

FIG. 16 is a process 440 for installing a threaded extension tube. Process 400 will now be described with reference to FIGS. 1-5, 8-14, and 16. After the thermal sleeve 10, 110 is removed 442, the threaded extension tube 310 is installed 444. The extension tube 310 is torque-tightened 446 to the headed penetration nozzle 306 using a torque tool. The alignment of the extension tube 310 is calibrated 448. Retaining weld beads 352 are installed 450. A compressible guide sleeve 332 is installed 452 and finally the alignment of the extension tube 310 is calibrated 454. The installation is now complete and the extension tube 310 is in its final installed arrangement 456. Details of the extension tube installation process 440 will now be described in more detail.

Continuing with reference to FIG. 16, FIGS. 17 and 18 illustrate the installation process step 444 of the threaded extension tube 310. As shown in FIG. 17, the extension tube 310 comprising a threaded penetration adapter 320 is aligned with a threaded headed penetration nozzle 306 extending through the reactor vessel head 304. The threaded headed penetration nozzle 306 comprises a threaded end 307 with male threads 349 configured to threadably engage the female threads 348 of the threaded end of the threaded penetration adapter 320. As discussed above, the threaded penetration adapter 320 is coupled to the extension tube 310 by a weld 354. As shown in FIG. 18, the female threads 348 of the threaded end of the threaded penetration adapter 320 are threadably engaged with the female threads 348 of the threaded end of the threaded penetration adapter 320. male threads 349 of the threaded end 307 of the penetration nozzle with threaded head 306.

Continuing with reference to FIGS. 16-18, FIGS. 19 and 20 illustrate the application of torque 446 of the extension tube 310 to the headed penetration nozzle 306 using a torque tool 350.

Continuing with reference to FIGS.16-20, FIGS. 21-23 illustrate the calibration process 448 of the alignment of the extension tube 310 after it has been properly tightened 446 to the headed penetration nozzle 306, where FIG. 21 is a sectional view 520 of a calibration test of the alignment of the extension tube 310, FIG. 22 is a perspective view of a gauge 522 used in the calibration process 448, and FIG. 23 is a sectional view of the alignment of a drive rod 530 relative to the extension tube 310. The gauge 522 is inserted into the guide funnel 312, through the extension tube 310, the headed penetration nozzle 306 and into the CRDM housing 308. The gauge 522 is rotated to fit into the guide funnel 312. The alignment of the extension tube 310 is measured relative to a nominal centerline with a maximum allowable offset. from the nominal centerline. Datum A is measured at a point along extension tube 310 and at a first radial offset 524 extending radially from bore 522 located at the end of extension tube 310 near guide tube 312, a second radial offset 526 located within headed penetration nozzle 306 just outside the reactor vessel head 304, and a third radial offset 528 located within the CRDM housing 308. The amount of deviation from datum A is determined at each radial offset location 524, 526, 528. In FIG. 23 , the alignment of a drive rod 532 relative to the inlet of guide funnel 312 is shown.

Once the alignment of the extension tube 310 has been calibrated 448, the retaining weld beads 352 are installed 450. Continuing with reference to FIGS. 16-23, FIG. 24 illustrates the retaining weld beads 352 installed 450 between the threaded end 307 of the headed penetration nozzle 306 and the threaded penetration adapter 320 coupled to the extension tube 310 by a weld 354.

Following installation 450 of the retaining weld beads 352, the compressible guide sleeve 332 is installed 452. Continuing with reference to FIGS. 16-24, FIGS. 25-29 illustrate the installation process 452 of the compressible guide sleeve 332. As shown in FIG. 25, the three-leaf compressible flexible sections 342 of the compressible guide sleeve 332 are compressed to shrink the flanges 344 of the compressible flexible sections 342 to a size suitable for insertion into the guide funnel 312. FIG. 26 illustrates a compression tool 536 that may be employed to compress the compressible guide sleeve 332 prior to inserting the compressible guide sleeve 332 into the guide nozzle 312. FIG. 27 illustrates the compressible guide sleeve 332 in its compressed configuration inserted through the headed penetration nozzle 306 and the CRDM head adapter 337 such that the flanges 344 of the flexible sections 342 are compressed. 342 compressible flexible sections are positioned just above a countersink shoulder 536 defined within the CRDM head adapter section 337 of the headed penetration nozzle 306. In FIG. 28, the compressible flexible sections 342 of the compressible guide sleeve 332 are released such that the flanges 344 of the compressible flexible sections 342 engage the countersink shoulder 536 defined within the CRDM head adapter section 337 of the headed penetration nozzle 306. The countersink shoulder 534 retains the compressible guide sleeve 332 within the CRDM head adapter section 337 of the headed penetration nozzle 306. FIG. 29 illustrates the compressible guide sleeve 332 in its final installed state. A final calibration 454 of the extension tube 310 can now be performed.

Continuing with reference to FIGS. 16-29 , FIGS. 30-33 illustrate the final installed arrangement 456 of the extension tube 310. FIG. 30 is a sectional view of the reactor vessel head 304 illustrating the extension tube 310 coupled to the headed penetration nozzle 306 installed within the reactor vessel head 304. FIG. 31 is a detailed view of the installed extension tube 310 coupled to the headed penetration nozzle 306 showing the extension tube retaining welds 352. FIG. 32 is a sectional view of the extension tube 310 coupled to the headed penetration nozzle 306 installed within the reactor vessel head 304. FIG. 33 is an elevation view of the extension tube 310 coupled to the headed penetration nozzle 306 installed within the reactor vessel head 304.

FIG. 34 illustrates a headed penetrating nozzle 306 with threads 552 that are unusable due to wear, damage, or size mismatch. FIG. 35 is a sectional view of the headed penetrating nozzle 306 shown in FIG. 34. Referring now to FIGS. 17, 34, and 35, if the male threads 349 on the threaded end 307 of the CRDM headed penetrating nozzle 306 are unusable, due to wear, damage, or size mismatch, in one aspect, a threaded adapter 550 may be employed as an alternative. The threaded adapter 550 is welded 554 below the male threads 349 of the penetration nozzle with head 310. The threaded adapter 550 includes male threads 552 suitable for threaded coupling with the female thread 348 on the threaded adapter 320 of the extension tube 310.

Field installation of a 310 extension tube becomes more complicated in nuclear plants without CRDM housings comprising 306 threaded-head penetration nozzles. Additional field machining would be required to prepare the unthreaded CRDM housing for welding, as well as to perform post-weld cleaning. The 310 extension tube design remains common between threaded and unthreaded CRDM housings. A process for installing a 310 extension tube into an unthreaded CRDM housing is described below.

FIG. 36 is a process 600 for installing an extension tube into an unthreaded CRDM housing. Referring also to FIGS. 37-39, process 600 begins with machining 602 of an unthreaded CRDM housing 650. In other words, the CRDM housing 650 does not include a threaded headed penetration nozzle with a threaded end 307 with male threads 349 as described with reference to FIGS. 3-35. FIG. 37 is a sectional view of an unthreaded CRDM housing 650 prior to machining. Machining step 602 involves preparing face 652 (FIG. 37, pre-machined) of the non-threaded CRDM housing geometry 650 for machine welding and backing out bore ID 654 of the non-threaded CRDM housing 650. FIG. 38 is a sectional view of the non-threaded CRDM housing 650 after machining 602. FIG. 39 is a detail view of the sectional view of the non-threaded CRDM housing shown in FIG. 38. As shown in FIGS. 38 and 39, face 656 (post-machined) of the non-threaded CRDM housing 650 is back-machined to remove radii and install the preparation weld. FIG. 39 shows a detail view of the machined face 656 of the non-threaded CRDM housing 650.

FIG. 41 illustrates a space 668 defined between the machined end face 656 of the unthreaded CRDM housing 650 and the unthreaded end 654 of the threaded adapter 660. With continued reference to FIGS. 36-39 and with reference also to FIGS. 14 and 40-41, the next step in the process 600 is to install and align 604 a threaded adapter 660 to the machined unthreaded CRDM housing 650. As shown in FIG. 40, threaded adapter 660 comprises male threads 662 sized and configured to receive female threads 348 of extension tube 310 (see FIG. 14, for example) and an unthreaded end 664 is configured to abut machined end face 656 of unthreaded CRDM housing 650. Threaded adapter 660 also defines a bore 670. As shown in FIG. 41, a space 668 is defined between the machined end face 656 of unthreaded CRDM housing 650 and the unthreaded end of threaded adapter 660.

FIG. 42 illustrates the threaded adapter 660 attached to the unthreaded CRDM housing 650. With continued reference to FIGS. 36-41, and also referring to FIG. 42, the next step in the process 600 is to join 606 the threaded adapter 660 to the unthreaded CRDM housing 650. In one aspect, the threaded adapter 660 is joined 606 to the CRDM housing by a penetration welding technique to form a joint 672. In one aspect, the threaded adapter 660 may be joined 606 to the unthreaded CRDM housing 650 by a full penetration weld joining 606 the threaded adapter 660 to the unthreaded CRDM housing 650 with no gaps between the filler material and the roots of the joint 672. In one aspect, the threaded adapter 660 may be welded to the unthreaded CRDM housing 650 and this may be performed using a specialized semi-automatic gas tungsten arc welding (GTAW) head, for example.

FIG. 43 illustrates machined bores 654, 670 defined by the non-threaded CRDM housing and the threaded adapter. With continued reference to FIGS. 36-42, and also with reference to FIG. 43, the next step in the process 600 is to machine 608 the bore 670 defined by the threaded adapter 660 and/or the bore 654 defined by the non-threaded CRDM housing 650. This step removes an integral backup ring/alignment ring.

FIG. 44 illustrates a machined/ground OD 674 of joint 672. With continuing reference to FIGS. 36-43, and also referring to FIG. 44, the next step in process 600 is to machine/ground 610 the OD 674 of joint 672, such as the penetration weld cap, for inspections. FIGS. 45 and 46 show the threaded adapter 660 attached to the unthreaded CRDM housing 650 installed below the reactor vessel head 304 and ready to receive the extension tube 310. FIG. 47 illustrates the threaded adapter 320 of the extension tube 310 installed in the threaded adapter attached to the unthreaded CRDM housing from below the reactor vessel head 304. With continuing reference to FIGS. 36-46, and also referring to FIGS. 14 and 47, the next step in process 600 is to install threaded adapter 320 of extension tube 310 into threaded adapter 660 attached to the unthreaded CRDM housing from below reactor vessel head 304. This step includes screwing and torqueing extension tube 310 into threaded adapter 660 in a manner similar to that described above with reference to 17-20.

FIG. 48 illustrates retaining weld beads 674 between threaded adapter 320 of extension tube 310 and threaded adapter 660 of unthreaded CRDM housing 650. Continuing with reference to FIGS. 36-47 , and also referring to FIGS. 14 and 48 , the next step in process 600 is installing 614 retaining weld beads 674. Process 600 may comprise installing a guide funnel 312 as described above with reference to 8-14, for example. Process 600 may further comprise calibrating the alignment of the extension tube using the same process described above with reference to FIGS. 21-23 , for example. Process 600 may further comprise installing a compressible guide sleeve 332 using the same process described above with reference to FIGS. 25-29 , for example.

1

Although certain aspects have been illustrated and described herein for descriptive purposes, a wide variety of alternative and/or equivalent aspects or implementations designed to achieve the same purposes may be substituted for the aspects shown and described without departing from the scope of the invention as defined in the claims. This application is intended to cover any adaptation or variation of the embodiments set forth herein.

Claims (17)

1. A method for installing an extension tube (310) in a nuclear reactor (2) comprising a control rod drive mechanism, CRDM, a housing (8) with a threaded head penetration nozzle (306) and a thermal sleeve (10) disposed therein, the method comprising: remove the thermal sleeve (10) from the threaded head penetration nozzle (306); aligning an extension tube (310) with a threaded end (307) of the threaded head penetration nozzle (306), the extension tube comprising a threaded end (348) and a non-threaded end, the threaded end (348) being sized and configured to threadably engage the threaded head penetration nozzle (306); screwing the threaded end (348) of the extension tube (310) to the threaded end (307) of the threaded head penetration nozzle (306); applying a tightening torque on the extension tube (310) to the threaded end (307) of the threaded head penetration nozzle (306); calibrate the alignment of the extension tube (310) with respect to the threaded head penetration nozzle (306); installing retaining weld beads (352) between the extension tube (310) and the threaded end (307) of the threaded head penetration nozzle (306); and Install a guide funnel (312) onto the unthreaded end of the extension tube (310). 2. The method of claim 1, comprising installing a compressible guide sleeve (332) in the CRDM housing (8). 3. The method of claim 2, wherein installing the compressible guide sleeve (332) into the CRDM housing (8) comprises: compress the compressible guide sleeve (332); inserting the compressed compressible guide sleeve (332) into the guide funnel, through the extension tube, the threaded head penetration nozzle (306), and the CRDM housing (8); and releasing the compression of the compressible guide sleeve (332) to retainably couple the compressible guide sleeve to the CRDM housing. 4. The method of any of claim 3, wherein the compressible guide sleeve (332) comprises multi-leaf compressible flexible sections (342), wherein each of the multi-leaf compressible flexible sections comprises a flange (344), the method comprising: compressing the multi-leaf compressible flexible sections to contract the flanges before inserting the compressed guide sleeve into the guide funnel, and releasing the compression of the compressible guide sleeve after insertion into the CRDM housing to release the flanges to engage a countersunk shoulder (536) defined by the CRDM housing. 5. A method for installing an extension tube (310) in a nuclear reactor (2) comprising a control rod drive mechanism, CRDM, a housing (650) with a non-threaded head penetration nozzle and a thermal sleeve (10) disposed therein, the method comprising: remove the thermal sleeve (10) from the non-threaded head penetration nozzle; machine the threadless head penetration nozzle of the CRDM housing (650); installing and aligning a threaded adapter (660) to the machined end of the CRDM housing's unthreaded head penetration nozzle (650); attach the threaded adapter (660) to the machined end of the unthreaded head penetration nozzle of the CRDM housing (650); machining a hole (654) defined by the threadless head penetration nozzle of the CRDM housing (650); machining a hole (670) defined by the threaded adapter (660); machining an outer diameter of a gasket (672) between the machined end of the CRDM housing unthreaded head penetration nozzle (650) and the threaded adapter (660); installing the extension tube (310) into the threaded adapter (660); and Install retaining weld beads (676) between the extension tube (310) and the threaded adapter (660). 6. The method of claim 5, wherein machining the threadless head penetration nozzle of the CRDM housing (650) comprises: preparing a face (656) of the non-threaded head penetration nozzle of the CRDM housing (650); and back off an inner diameter of the hole (654) defined by the penetration nozzle of the unthreaded head of the CRDM housing (650). 7. The method of claim 5, wherein joining the threaded adapter to the machined end of the unthreaded head penetration nozzle of the CRDM housing (650) comprises performing a penetration welding technique to form the joint (672). 8. The method of claim 7, wherein joining the threaded adapter (660) to the machined end of the unthreaded head penetration nozzle of the CRDM housing (650) comprises performing a full penetration welding technique to form the joint (672). 9. The method of claim 5, wherein installing the extension tube (310) into the threaded adapter (660) comprises: screw the extension tube (310) into the threaded adapter (660); and apply torque to the extension tube (310) on the threaded adapter (660). 10. The method of claim 5, comprising calibrating an alignment of the extension tube (310) with respect to the non-threaded head penetration nozzle (650). 11. The method of claim 5, comprising installing a guide funnel (312) on an unthreaded end of the extension tube (310). 12. The method of claim 11, comprising installing a compressible guide sleeve (332) in the CRDM housing (650). 13. The method of claim 12, wherein installing the compressible guide sleeve into the CRDM housing (650) comprises: compress the compressible guide sleeve (332); inserting the compressed compressible guide sleeve (332) through the extension tube (310), the non-threaded head penetration nozzle, and the CRDM housing (650); and releasing the compression of the compressible guide sleeve (332) to retainably couple the compressible guide sleeve (332) to the CRDM housing (650). 14. The method of claim 13, wherein the compressible guide sleeve (332) comprises multi-leaf compressible flexible sections (342), wherein each of the multi-leaf compressible flexible sections comprises a flange (344), the method comprising: compressing the multi-leaf compressible flexible sections to contract the flanges before inserting the compressed compressible guide sleeve (332) into the extension tube (320); and releasing the compression of the compressible guide sleeve (332) after insertion into the CRDM housing (650) to release the flanges to engage a countersunk shoulder (536) defined by the CRDM housing (650). 15. The method of any of claim 4 or 14, comprising performing a final calibration of an alignment of the extension tube (310). 16. The method of any of claim 3 or 15, wherein the compressible guide sleeve (332) is inserted into the guide funnel (312) from a position below the reactor vessel head of the nuclear reactor (2). 17. The method of any one of claims 1 or 5, wherein the extension tube (310) is installed from a position below a reactor vessel head of the nuclear reactor (2). 1